Effects of Different Dietary Additives on Growth Performance and Immune Responses in Juvenile Amur Catfish Silurus asotus

Abstract

A feeding trial was conducted to evaluate effects of three dietary additives on growth performance and immune responses in juvenile Amur Catfish Silurus asotus and identify the one that has more positive responses with a lower cost. A basal commercial diet was used as a control (CONT) from which four other diets were prepared by supplementing 0.4% Song-gang® stone (SG), 0.05% Yucca meal (YM), 0.05% β-glucan (BG) and combining 0.04% SG and 0.05% BG (SG+BG). Triplicate groups of fish (initial body weight 4.95±0.05g) were fed one of the test diets between 3-5% of body weight for 8 weeks. At the end of the feeding trial, weight gain (WG), specific growth rate (SGR), feed efficiency (FE) and protein efficiency ratio (PER) of fish fed SG and SG+BG diets were significantly higher than those of fish fed BG and CONT diets (p<0.05) but not significantly different from fish fed YM diet. Lysozyme activity in fish fed SG, YM, and SG+BG diets were significantly higher than those of fish fed CONT but not significantly different form those of fish fed BG diet while SOD values were significantly higher among fish fed SG, YM, BG and SG+BG than those of fish fed CONT. After 14 days of intraperitoneal injection with Edwardsiella tarda bacterium, cumulative survival rates of fish fed SG and SG+BG were significantly higher than those of fish fed BG and CONT diets but not significantly different from those of fish fed YM diet. However, there were no significant differences among those of fish fed YM, BG and CONT. Crude protein content was significantly higher while crude lipid content was significantly lower (P<0.05) in fish fed YM diet than those of fish fed the other diets. Serum parameters in fish fed all the experimental diets were not significantly affected. Based on WG, SGR, FE, PER, Lysozyme, SOD and resistance against bacteria, dietary Song-gang stone® and SG+BG could have more positive responses in juvenile Amur catfish Silurus asotus. However, Song-gang® stone is proposed to be a cheaper dietary additive contributing ₩4.00/kg of diet.